Diarmuid O'Hegarty was an Irish

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 revolutionary and civil servant.

Born in Cork

Cork (city)

Cork is the second largest city in the Republic of Ireland and the island of Ireland's third most populous city. It is the principal city and administrative centre of County Cork and the largest city in the province of Munster. Cork has a population of 119,418, while the addition of the suburban...

, O'Hegarty was prominent in the re-organisation of the Irish Volunteers

Irish Volunteers

The Irish Volunteers was a military organisation established in 1913 by Irish nationalists. It was ostensibly formed in response to the formation of the Ulster Volunteers in 1912, and its declared primary aim was "to secure and maintain the rights and liberties common to the whole people of Ireland"...

 after the 1916 Easter Rising

Easter Rising

The Easter Rising was an insurrection staged in Ireland during Easter Week, 1916. The Rising was mounted by Irish republicans with the aims of ending British rule in Ireland and establishing the Irish Republic at a time when the British Empire was heavily engaged in the First World War...

. He was vice-commandant of the Irish Republican Army's

Irish Republican Army

The Irish Republican Army was an Irish republican revolutionary military organisation. It was descended from the Irish Volunteers, an organisation established on 25 November 1913 that staged the Easter Rising in April 1916...

 1st Dublin Brigade and became IRA Director of Organisation in 1920.

Supportive of the Anglo-Irish Treaty

Anglo-Irish Treaty

The Anglo-Irish Treaty , officially called the Articles of Agreement for a Treaty Between Great Britain and Ireland, was a treaty between the Government of the United Kingdom of Great Britain and Ireland and representatives of the secessionist Irish Republic that concluded the Irish War of...

, in September 1922, following the death of Michael Collins

Michael Collins (Irish leader)

Michael "Mick" Collins was an Irish revolutionary leader, Minister for Finance and Teachta Dála for Cork South in the First Dáil of 1919, Director of Intelligence for the IRA, and member of the Irish delegation during the Anglo-Irish Treaty negotiations. Subsequently, he was both Chairman of the...

, he was appointed commandant general, a member of the Army Council, and Director of Intelligence of the National Army

Irish Defence Forces

The armed forces of Ireland, known as the Defence Forces encompass the Army, Naval Service, Air Corps and Reserve Defence Force.The current Supreme Commander of the Irish Defence forces is His Excellency Michael D Higgins in his role as President of Ireland...

In March 1923, he was appointed Secretary to the Executive Council

Executive Council of the Irish Free State

The Executive Council was the cabinet and de facto executive branch of government of the 1922–1937 Irish Free State. Formally, the role of the Executive Council was to "aid and advise" the Governor-General who would exercise the executive authority on behalf of the King...

 of the Irish Free State

Irish Free State

The Irish Free State was the state established as a Dominion on 6 December 1922 under the Anglo-Irish Treaty, signed by the British government and Irish representatives exactly twelve months beforehand...

.